Author:

Peng Liu(Shanghai Institute of Optics \& Fine Mechanics, CAS)

Molecules can be strongly aligned non-adiabatically by using the
two-pulse
femtosecond laser field with an optimized delay time. We propose
a novel
strategy to determine the optimal timings of the two laser pulses
to modify
the molecular rotational wave packet, by which the molecular
alignment
generated by the first pulse is suppressed or enhanced by
adjusting the
respective delay times. This provides a way to actively control the
molecular rotational wave packet. The underlying physics
attributes to the
selective population transfer of molecular rotations.
We also experimentally investigate the high-order harmonic
generation (HHG)
from aligned CO$_{2}$ molecules and demonstrate that the modulation
inversion of harmonic yield with respect to molecular alignment
can be
altered dramatically by the intensity of the driving laser pulse.
The laser
field dependent inversion can be explained by the shift angular
distribution
of harmonic emission calculated with the strong field
approximation (SFA)
model including a ground state depletion factor. The calculation
result on
angular distributions using SFA model is consistent with the
experimental
observations for the 19$^{th}$ to 27$^{th}$ harmonics.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2010.MAR.K1.277